The phrase "picking up the tab" refers to the act of paying for someone else's expenses, usually in a social or business setting. The antonym for this phrase would be "passing the buck," which means to avoid taking responsibility by shifting it to someone else. Other antonyms for "picking up the tab" can include "leaving the bill unpaid," "letting someone else foot the bill," or "bailing on the payment." These antonyms denote an unwillingness to pay, avoidance of responsibility or an act of neglect. When it comes to a social setting or business deal, it is always best to avoid using these antonyms and being responsible for your own expenses.